A large majority of people move for far more compelling reasons, like jobs, the cost of housing, family ties or a warmer climate. At least three recent academic studies have demonstrated that the number of people who move for tax reasons is negligible, even among the wealthy.

One of those studies, "Tax Flight Is a Myth", is particularly notable. It finds that, although there are huge discrepancies between tax rates in different US states, under a third of US citizens change their state of residence over their lifetime.

Some people certainly do move for financial reasons – only not the ones that we might assume. New Jersey introduced an annual additional tax on those with incomes over $500,000 in 2004; by the end of 2007, no more than 70 tax filers had left the state and New Jersey was a net $3.75bn better off than under the old tax system.

It is property prices that are much more important. Consider the case of Florida: with no state income tax, you might expect the state to be flooded with those wishing to escape taxes. Except, in the late 2000s, Florida’s population actually declined. Lack of state income taxation might have been appealing, but it couldn’t make up for Florida’s rapidly rising housing prices.

What can the UK learn from these studies? Retaining the 50p tax rate probably wouldn’t have led to the wealth exodus that George Osborne feared. And for something labelled “socialist” the proposed mansion tax is striking in its caution: someone with a house worth £3m would pay only £10,000 extra a year. It wouldn’t raise the redistributive sums the left hopes, and nor would it punish successful businessmen as the right fears.